1. Field of the invention
The present invention concerns an output management circuit suitable for a programmable control system such as a programmable automatic controller or like device.
2. Description of the prior art
The patent FR-2 607 274 describes a programmable automatic controller input-output management circuit comprising an input-output management unit connected to a processor unit adapted to determine the state of output channels according to the state of input channels with reference to a predefined program and an output circuit which comprises a serial to parallel converter having a serial input connected to a serial output of the management unit and parallel outputs connected via a power stage to respective output channels, the output circuit further comprising control and monitor logic.
In this prior art, the output circuit does not benefit from the simplification and the saving in space achieved by parallel to serial conversion of the input data. Also, it would be highly beneficial to make it possible to sent to the management unit information relating to the state of the output channels, in particular to indicate if any channel is open-circuit or short-circuited, or information relating to the absence of voltage at pre-actuators or at the circuit itself.
An object of the invention is to simplify, in a programmable controller system, the routing to appropriate data output channels and the returning to the management unit of control signals contributing to establishing the reliability of communications and to supervising current and/or voltage faults affecting the output lines.
Another object of the invention is to provide dialogue via two up and down serial links between an output management unit or an input-output management unit and an output circuit using frames preferably having a uniform format.
A further object is to confer upon a local or remote output management circuit great flexibility of use by configuring it very simply so that it can be operated in various different operating modes, in particular an "output" mode and an "input" mode, or so that it can be used equally in digital and analog applications.
A further object is to create an output management circuit which lends itself well to implementation in integrated circuit form.